I have collections of entities that I need to sort depending on their dependencies to each other. Here's an example because it's fairly tough to explain:
public class A : I {
private B objB;
public B propB { get{ return objB; } }
// Some other fields and properties.
}
public class B : I { /* Some fields and properties. */ }
public class C : I {
private A objA;
public A propA { get{ return objA; } }
// Some other fields and properties.
}
public interface I {}
The thing is that I need to import data into collections of those types but I need to import in a certain order because if I import A objects first, I will not be able to link the corresponding B since it won't exist yet.
So what I'd like is to sort my collections in a way that all dependencies are imported in the right order (There are no circular dependencies). I can't figure out a linq statement that will do that though.
lists.OrderBy(l => l. ??? );
I was thinking maybe get a list typesList of all the types T of the List<T> in lists and somehow use reflection to count how many fields in T are in typesList but that seems... inefficient ?
EDIT: Realized the wording of my structure is a bit vague.
Basically lists is a List<List<I>>. Here's a results example:
List<List<I>> collections before:
-List<A>
-List<C>
-List<B>
List<List<I>> collections after:
-List<B> // B has 0 dependency to B or C.
-List<A> // A has 1 dependency to B.
-List<C> // C has 1 dependency to A.
The easiest way I know to do it is build up a new collection, as you build it up see if you see any known types in the class. If you do see a known type put it it just before the first sighting or put it at the end if no known types were found. Once you have that collection just enumerate the collection in reverse order and it will the items in reverse dependency order.
The below example is used like
var sortedLists = lists.OrderByTypeDependency();
How to implement the LINQ style extension method:
static class ExtensionMethods
{
public static IEnumerable<T> OrderByTypeDependency<T>(this IEnumerable<T> items)
{
LinkedList<T> knownItems = new LinkedList<T>();
foreach (var item in items)
{
var itemType = item.GetType();
var itemPropertyTypes =
itemType.GetProperties(BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance)
.Select(x => x.PropertyType);
var itemFieldTypes =
itemType.GetFields(BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance)
.Select(x => x.FieldType);
//Create a set of all types internal to type we are checking on.
HashSet<Type> itemChildTypes = new HashSet<Type>(itemPropertyTypes.Concat(itemFieldTypes));
bool found = false;
for (var knownItemNode = knownItems.First; knownItemNode != null; knownItemNode = knownItemNode.Next)
{
var knownItemType = knownItemNode.Value.GetType();
if (itemType == knownItemType || itemChildTypes.Contains(knownItemType))
{
knownItems.AddBefore(knownItemNode, item);
found = true;
break;
}
}
if (!found)
{
knownItems.AddLast(item);
}
}
//output the result in reverse order.
for (var knownItemNode = knownItems.Last; knownItemNode != null; knownItemNode = knownItemNode.Previous)
{
yield return knownItemNode.Value;
}
}
}
EDIT: it was not clear if you where passing in a list of types or a list of objects. If you are passing in a list of types it is only a few small tweaks to the code, just drop the two .GetType() calls and switch from generics to only accepting IEnumerable<Type>
static class ExtensionMethods
{
public static IEnumerable<Type> OrderByTypeDependency(this IEnumerable<Type> items)
{
LinkedList<Type> knownItems = new LinkedList<Type>();
foreach (var item in items)
{
var itemType = item;
var itemPropertyTypes =
itemType.GetProperties(BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance)
.Select(x => x.PropertyType);
var itemFieldTypes =
itemType.GetFields(BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance)
.Select(x => x.FieldType);
//Create a set of all types internal to type we are checking on.
HashSet<Type> itemChildTypes = new HashSet<Type>(itemPropertyTypes.Concat(itemFieldTypes));
bool found = false;
for (var knownItemNode = knownItems.First; knownItemNode != null; knownItemNode = knownItemNode.Next)
{
var knownItemType = knownItemNode.Value;
if (itemType == knownItemType || itemChildTypes.Contains(knownItemType))
{
knownItems.AddBefore(knownItemNode, item);
found = true;
break;
}
}
if (!found)
{
knownItems.AddLast(item);
}
}
for (var knownItemNode = knownItems.Last; knownItemNode != null; knownItemNode = knownItemNode.Previous)
{
yield return knownItemNode.Value;
}
}
}
UPDATE:
Per your update to the question, as long as the inner lists hold the same type of object in the list so we can just check the first item in the list to find it's type this modification of the original code will do the sorting you need.
static class ExtensionMethods
{
public static IEnumerable<T> OrderByTypeDependency<T>(this IEnumerable<T> outerList)
where T: IList
{
LinkedList<T> knownItems = new LinkedList<T>();
foreach (var innerList in outerList)
{
if(innerList.Count == 0)
continue;
var itemType = innerList[0].GetType();
var itemPropertyTypes = itemType.GetProperties(BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance)
.Select(x => x.PropertyType);
var itemFieldTypes = itemType.GetFields(BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance)
.Select(x => x.FieldType);
//Create a set of all types internal to type we are checking on.
HashSet<Type> itemChildTypes = new HashSet<Type>(itemPropertyTypes.Concat(itemFieldTypes));
bool found = false;
for (var knownItemNode = knownItems.First; knownItemNode != null; knownItemNode = knownItemNode.Next)
{
var knownItemType = knownItemNode.Value[0].GetType();
if (itemType == knownItemType || itemChildTypes.Contains(knownItemType))
{
knownItems.AddBefore(knownItemNode, innerList);
found = true;
break;
}
}
if (!found)
{
knownItems.AddLast(innerList);
}
}
for (var knownItemNode = knownItems.Last; knownItemNode != null; knownItemNode = knownItemNode.Previous)
{
yield return knownItemNode.Value;
}
}
}
I have 2 instances of the same objects, o1, and o2. If I am doing things like
if (o1.property1 != null) o1.property1 = o2.property1
for all the properties in the object. What would be the most efficient way to loop through all properties in an Object and do that? I saw people using PropertyInfo to check nulll of the properties but it seems like they could only get through the PropertyInfo collection but not link the operation of the properties.
Thanks.
You can do this with reflection:
public void CopyNonNullProperties(object source, object target)
{
// You could potentially relax this, e.g. making sure that the
// target was a subtype of the source.
if (source.GetType() != target.GetType())
{
throw new ArgumentException("Objects must be of the same type");
}
foreach (var prop in source.GetType()
.GetProperties(BindingFlags.Instance |
BindingFlags.Public)
.Where(p => !p.GetIndexParameters().Any())
.Where(p => p.CanRead && p.CanWrite))
{
var value = prop.GetValue(source, null);
if (value != null)
{
prop.SetValue(target, value, null);
}
}
}
Judging from your example i think your looking for something like this:
static void CopyTo<T>(T from, T to)
{
foreach (PropertyInfo property in typeof(T).GetProperties())
{
if (!property.CanRead || !property.CanWrite || (property.GetIndexParameters().Length > 0))
continue;
object value = property.GetValue(to, null);
if (value != null)
property.SetValue(to, property.GetValue(from, null), null);
}
}
If you are going to use this many times, you could use a compiled expression for better performance:
public static class Mapper<T>
{
static Mapper()
{
var from = Expression.Parameter(typeof(T), "from");
var to = Expression.Parameter(typeof(T), "to");
var setExpressions = typeof(T)
.GetProperties()
.Where(property => property.CanRead && property.CanWrite && !property.GetIndexParameters().Any())
.Select(property =>
{
var getExpression = Expression.Call(from, property.GetGetMethod());
var setExpression = Expression.Call(to, property.GetSetMethod(), getExpression);
var equalExpression = Expression.Equal(Expression.Convert(getExpression, typeof(object)), Expression.Constant(null));
return Expression.IfThen(Expression.Not(equalExpression), setExpression);
});
Map = Expression.Lambda<Action<T, T>>(Expression.Block(setExpressions), from, to).Compile();
}
public static Action<T, T> Map { get; private set; }
}
And use it like this:
Mapper<Entity>.Map(e1, e2);
I'm new to lambda. So excuse me if my question is simple.
I have a method that uses reflection to set a property on some types:
public void WriteId(object obj, int id) {
var type = obj.GetType();
var prop = type.GetProperties(BindingFlags.Public | BindingFlags.Instance)
.Where(p => p.CanRead && p.CanWrite)
.Where(p => p.Name == "Id")
.Where(p.PropertyType == typeof(int))
.FirstOrDefault();
if(prop != null)
prop.SetValue(obj, id, null);
}
Can you show me please how can I create a lambda that do same job? Actually I want to create a lambda for each type, compile it, and cache it. Thanks in advance.
I would install FastMember from NuGet, and then use:
var wrapped = ObjectAccessor.Create(obj);
obj["Id"] = id;
which does pretty much what you say, except it happens to use ILGenerator via TypeBuilder (rather than Expression) - but all the caching etc is there.
A second cheaky approach is to get dynamic to do it all for you:
((dynamic)obj).Id = id;
But if you want to use Expression for other reasons:
using System;
using System.Linq.Expressions;
static class Program
{
static void Main()
{
var obj = new Foo { Id = 2 };
WriteId(obj, 6);
Console.WriteLine(obj.Id); // 6
}
private static class SneakyCache<T>
{
public static readonly Action<T, int> SetId;
static SneakyCache()
{
var obj = Expression.Parameter(typeof(T), "obj");
var id = Expression.Parameter(typeof(int), "id");
SetId = Expression.Lambda<Action<T, int>>(
Expression.Assign(Expression.Property(obj, "Id"), id),
obj, id).Compile();
}
}
public static void WriteId<T>(T obj, int id) where T : class
{
SneakyCache<T>.SetId(obj, id);
}
}
class Foo
{
public int Id { get; set; }
}
Given the following objects:
public class Customer {
public String Name { get; set; }
public String Address { get; set; }
}
public class Invoice {
public String ID { get; set; }
public DateTime Date { get; set; }
public Customer BillTo { get; set; }
}
I'd like to use reflection to go through the Invoice to get the Name property of a Customer. Here's what I'm after, assuming this code would work:
Invoice inv = GetDesiredInvoice(); // magic method to get an invoice
PropertyInfo info = inv.GetType().GetProperty("BillTo.Address");
Object val = info.GetValue(inv, null);
Of course, this fails since "BillTo.Address" is not a valid property of the Invoice class.
So, I tried writing a method to split the string into pieces on the period, and walk the objects looking for the final value I was interested in. It works okay, but I'm not entirely comfortable with it:
public Object GetPropValue(String name, Object obj) {
foreach (String part in name.Split('.')) {
if (obj == null) { return null; }
Type type = obj.GetType();
PropertyInfo info = type.GetProperty(part);
if (info == null) { return null; }
obj = info.GetValue(obj, null);
}
return obj;
}
Any ideas on how to improve this method, or a better way to solve this problem?
EDIT after posting, I saw a few related posts... There doesn't seem to be an answer that specifically addresses this question, however. Also, I'd still like the feedback on my implementation.
I use following method to get the values from (nested classes) properties like
"Property"
"Address.Street"
"Address.Country.Name"
public static object GetPropertyValue(object src, string propName)
{
if (src == null) throw new ArgumentException("Value cannot be null.", "src");
if (propName == null) throw new ArgumentException("Value cannot be null.", "propName");
if(propName.Contains("."))//complex type nested
{
var temp = propName.Split(new char[] { '.' }, 2);
return GetPropertyValue(GetPropertyValue(src, temp[0]), temp[1]);
}
else
{
var prop = src.GetType().GetProperty(propName);
return prop != null ? prop.GetValue(src, null) : null;
}
}
Here is the Fiddle: https://dotnetfiddle.net/PvKRH0
I know I'm a bit late to the party, and as others said, your implementation is fine
...for simple use cases.
However, I've developed a library that solves exactly that use case, Pather.CSharp.
It is also available as Nuget Package.
Its main class is Resolver with its Resolve method.
You pass it an object and the property path, and it will return the desired value.
Invoice inv = GetDesiredInvoice(); // magic method to get an invoice
var resolver = new Resolver();
object result = resolver.Resolve(inv, "BillTo.Address");
But it can also resolve more complex property paths, including array and dictionary access.
So, for example, if your Customer had multiple addresses
public class Customer {
public String Name { get; set; }
public IEnumerable<String> Addresses { get; set; }
}
you could access the second one using Addresses[1].
Invoice inv = GetDesiredInvoice(); // magic method to get an invoice
var resolver = new Resolver();
object result = resolver.Resolve(inv, "BillTo.Addresses[1]");
I actually think your logic is fine. Personally, I would probably change it around so you pass the object as the first parameter (which is more inline with PropertyInfo.GetValue, so less surprising).
I also would probably call it something more like GetNestedPropertyValue, to make it obvious that it searches down the property stack.
You have to access the ACTUAL object that you need to use reflection on. Here is what I mean:
Instead of this:
Invoice inv = GetDesiredInvoice(); // magic method to get an invoice
PropertyInfo info = inv.GetType().GetProperty("BillTo.Address");
Object val = info.GetValue(inv, null);
Do this (edited based on comment):
Invoice inv = GetDesiredInvoice(); // magic method to get an invoice
PropertyInfo info = inv.GetType().GetProperty("BillTo");
Customer cust = (Customer)info.GetValue(inv, null);
PropertyInfo info2 = cust.GetType().GetProperty("Address");
Object val = info2.GetValue(cust, null);
Look at this post for more information:
Using reflection to set a property of a property of an object
In hopes of not sounding too late to the party, I would like to add my solution:
Definitely use recursion in this situation
public static Object GetPropValue(String name, object obj, Type type)
{
var parts = name.Split('.').ToList();
var currentPart = parts[0];
PropertyInfo info = type.GetProperty(currentPart);
if (info == null) { return null; }
if (name.IndexOf(".") > -1)
{
parts.Remove(currentPart);
return GetPropValue(String.Join(".", parts), info.GetValue(obj, null), info.PropertyType);
} else
{
return info.GetValue(obj, null).ToString();
}
}
You don't explain the source of your "discomfort," but your code basically looks sound to me.
The only thing I'd question is the error handling. You return null if the code tries to traverse through a null reference or if the property name doesn't exist. This hides errors: it's hard to know whether it returned null because there's no BillTo customer, or because you misspelled it "BilTo.Address"... or because there is a BillTo customer, and its Address is null! I'd let the method crash and burn in these cases -- just let the exception escape (or maybe wrap it in a friendlier one).
Here is another implementation that will skip a nested property if it is an enumerator and continue deeper. Properties of type string are not affected by the Enumeration Check.
public static class ReflectionMethods
{
public static bool IsNonStringEnumerable(this PropertyInfo pi)
{
return pi != null && pi.PropertyType.IsNonStringEnumerable();
}
public static bool IsNonStringEnumerable(this object instance)
{
return instance != null && instance.GetType().IsNonStringEnumerable();
}
public static bool IsNonStringEnumerable(this Type type)
{
if (type == null || type == typeof(string))
return false;
return typeof(IEnumerable).IsAssignableFrom(type);
}
public static Object GetPropValue(String name, Object obj)
{
foreach (String part in name.Split('.'))
{
if (obj == null) { return null; }
if (obj.IsNonStringEnumerable())
{
var toEnumerable = (IEnumerable)obj;
var iterator = toEnumerable.GetEnumerator();
if (!iterator.MoveNext())
{
return null;
}
obj = iterator.Current;
}
Type type = obj.GetType();
PropertyInfo info = type.GetProperty(part);
if (info == null) { return null; }
obj = info.GetValue(obj, null);
}
return obj;
}
}
based on this question and on
How to know if a PropertyInfo is a collection
by Berryl
I use this in a MVC project to dynamically Order my data by simply passing the Property to sort by
Example:
result = result.OrderBy((s) =>
{
return ReflectionMethods.GetPropValue("BookingItems.EventId", s);
}).ToList();
where BookingItems is a list of objects.
> Get Nest properties e.g., Developer.Project.Name
private static System.Reflection.PropertyInfo GetProperty(object t, string PropertName)
{
if (t.GetType().GetProperties().Count(p => p.Name == PropertName.Split('.')[0]) == 0)
throw new ArgumentNullException(string.Format("Property {0}, is not exists in object {1}", PropertName, t.ToString()));
if (PropertName.Split('.').Length == 1)
return t.GetType().GetProperty(PropertName);
else
return GetProperty(t.GetType().GetProperty(PropertName.Split('.')[0]).GetValue(t, null), PropertName.Split('.')[1]);
}
if (info == null) { /* throw exception instead*/ }
I would actually throw an exception if they request a property that doesn't exist. The way you have it coded, if I call GetPropValue and it returns null, I don't know if that means the property didn't exist, or the property did exist but it's value was null.
public static string GetObjectPropertyValue(object obj, string propertyName)
{
bool propertyHasDot = propertyName.IndexOf(".") > -1;
string firstPartBeforeDot;
string nextParts = "";
if (!propertyHasDot)
firstPartBeforeDot = propertyName.ToLower();
else
{
firstPartBeforeDot = propertyName.Substring(0, propertyName.IndexOf(".")).ToLower();
nextParts = propertyName.Substring(propertyName.IndexOf(".") + 1);
}
foreach (var property in obj.GetType().GetProperties())
if (property.Name.ToLower() == firstPartBeforeDot)
if (!propertyHasDot)
if (property.GetValue(obj, null) != null)
return property.GetValue(obj, null).ToString();
else
return DefaultValue(property.GetValue(obj, null), propertyName).ToString();
else
return GetObjectPropertyValue(property.GetValue(obj, null), nextParts);
throw new Exception("Property '" + propertyName.ToString() + "' not found in object '" + obj.ToString() + "'");
}
I wanted to share my solution although it may be too late. This solution is primarily to check if the nested property exists. But it can be easily tweaked to return the property value if needed.
private static PropertyInfo _GetPropertyInfo(Type type, string propertyName)
{
//***
//*** Check if the property name is a complex nested type
//***
if (propertyName.Contains("."))
{
//***
//*** Get the first property name of the complex type
//***
var tempPropertyName = propertyName.Split(".", 2);
//***
//*** Check if the property exists in the type
//***
var prop = _GetPropertyInfo(type, tempPropertyName[0]);
if (prop != null)
{
//***
//*** Drill down to check if the nested property exists in the complex type
//***
return _GetPropertyInfo(prop.PropertyType, tempPropertyName[1]);
}
else
{
return null;
}
}
else
{
return type.GetProperty(propertyName, BindingFlags.IgnoreCase | BindingFlags.Public | BindingFlags.Instance);
}
}
I had to refer to few posts to come up with this solution. I think this will work for multiple nested property types.
My internet connection was down when I need to solve the same problem, so I had to 're-invent the wheel':
static object GetPropertyValue(Object fromObject, string propertyName)
{
Type objectType = fromObject.GetType();
PropertyInfo propInfo = objectType.GetProperty(propertyName);
if (propInfo == null && propertyName.Contains('.'))
{
string firstProp = propertyName.Substring(0, propertyName.IndexOf('.'));
propInfo = objectType.GetProperty(firstProp);
if (propInfo == null)//property name is invalid
{
throw new ArgumentException(String.Format("Property {0} is not a valid property of {1}.", firstProp, fromObject.GetType().ToString()));
}
return GetPropertyValue(propInfo.GetValue(fromObject, null), propertyName.Substring(propertyName.IndexOf('.') + 1));
}
else
{
return propInfo.GetValue(fromObject, null);
}
}
Pretty sure this solves the problem for any string you use for property name, regardless of extent of nesting, as long as everything's a property.
Based on the original code from #jheddings, I have created a extension method version with generic type and verifications:
public static T GetPropertyValue<T>(this object sourceObject, string propertyName)
{
if (sourceObject == null) throw new ArgumentNullException(nameof(sourceObject));
if (string.IsNullOrWhiteSpace(propertyName)) throw new ArgumentException(nameof(propertyName));
foreach (string currentPropertyName in propertyName.Split('.'))
{
if (string.IsNullOrWhiteSpace(currentPropertyName)) throw new InvalidOperationException($"Invalid property '{propertyName}'");
PropertyInfo propertyInfo = sourceObject.GetType().GetProperty(currentPropertyName);
if (propertyInfo == null) throw new InvalidOperationException($"Property '{currentPropertyName}' not found");
sourceObject = propertyInfo.GetValue(sourceObject);
}
return sourceObject is T result ? result : default;
}
I wrote a method that received one object type as the argument from the input and returns dictionary<string,string>
public static Dictionary<string, string> GetProperties(Type placeHolderType)
{
var result = new Dictionary<string, string>();
var properties = placeHolderType.GetProperties();
foreach (var propertyInfo in properties)
{
string name = propertyInfo.Name;
string description = GetDescriptionTitle(propertyInfo);
if (IsNonString(propertyInfo.PropertyType))
{
var list = GetProperties(propertyInfo.PropertyType);
foreach (var item in list)
{
result.Add($"{propertyInfo.PropertyType.Name}_{item.Key}", item.Value);
}
}
else
{
result.Add(name, description);
}
}
return result;
}
public static bool IsNonString(Type type)
{
if (type == null || type == typeof(string))
return false;
return typeof(IPlaceHolder).IsAssignableFrom(type);
}
private static string GetDescriptionTitle(MemberInfo memberInfo)
{
if (Attribute.GetCustomAttribute(memberInfo, typeof(DescriptionAttribute)) is DescriptionAttribute descriptionAttribute)
{
return descriptionAttribute.Description;
}
return memberInfo.Name;
}
public static object GetPropertyValue(object src, string propName)
{
if (src == null) throw new ArgumentException("Value cannot be null.", "src");
if (propName == null) throw new ArgumentException("Value cannot be null.", "propName");
var prop = src.GetType().GetProperty(propName);
if (prop != null)
{
return prop.GetValue(src, null);
}
else
{
var props = src.GetType().GetProperties();
foreach (var property in props)
{
var propInfo = src.GetType().GetProperty(property.Name);
if (propInfo != null)
{
var propVal = propInfo.GetValue(src, null);
if (src.GetType().GetProperty(property.Name).PropertyType.IsClass)
{
return GetPropertyValue(propVal, propName);
}
return propVal;
}
}
return null;
}
usage: calling part
var emp = new Employee() { Person = new Person() { FirstName = "Ashwani" } };
var val = GetPropertyValue(emp, "FirstName");
above can search the property value at any level
Try inv.GetType().GetProperty("BillTo+Address");